class Animal(object):
    pass

class Dog(Animal):

    def __init__(self,name):
        self.name=name

    
class Cat(Animal):

    def __init__(self,name):
        self.name=name

class Person(object):

    def __init__(self,name):
        self.name=name
        self.pet=None

class Employee(Person):

    def __init__(self,name,salary):
        super(Employee,self).__init__(name)
        self.salary=salary

class Fish(object):
    pass

class Salmon(Fish):
    pass

class Halibut(Fish):
    pass

rover=Dog("Rover")
satan=Cat("Satan")
mary=Person("Mary")
mary.pet=satan
frank=Employee("Frank",12000)
frank.pet=rover
flipper=Fish()
crouse=Salmon()
harry=Halibut()